BIRDS. 157 



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The ossification of the Sternum in the Pluvialinse is by three endosteal patches a right 

 and left " pleurosteon " and a " lophosteon ;" the latter bony centre, in (Edicnemus (six weeks old), 

 is shown in Plate XVI, fig. 22, magnified twenty diameters. The bony deposit (en.) is seen to 

 be in two layers, between which there are irregular marrow cavities (m. c.) : c. represents the 

 cartilage which is being metamorphosed, and p. the perichondrum. 



The Shoulder-girdle is very uniform throughout the whole of the large Pluvialine family ; 

 the scapiila is ensiform, moderately curved, flattened towards its pointed end, and has a blunt 

 meso-scapular process. The coracoid is relatively short, has a projecting head, and a large curled 

 meso-coracoid process, at the root of which is the usual foramen ; a narrow, flattened body, a 

 very arcuate articular base, and a well-developed epicoracoid hook. In many species, namely, 

 Vanellus, (Edicnemus, and Numenius, there is an inner epicoracoid process, the distal portion 

 of the arrested meso-coracoid bar. The furcula is U-shaped, strong, has its rami curved to 

 about one third of a circle, and its tips and shoulders thickened by the hourglass-shaped coraco- 

 scapular segment (see Plate XV, fig. 3, m. sc. s., p. cr. s.). These are, however, evidently ossified 

 directly from the clavicles. The interclavicle arises from behind the clavicular synostosis ; it is 

 moderately developed, thick, and semi-oval. The Sternum is also very uniform, on the whole ; 

 it is oblong, the length being about thrice that of the width ; it is widest in Hamatopus, and nar- 

 rowest in Totanus, Vanellus, and Scolopax gallinago. The outer margins are pinched in a little 

 behind the ribs, and then expand gently. There are, on an average, six pairs of condyles for the 

 sternal ribs, and these run far up the squarish costal processes. The coracoid grooves are 

 separated in front by the thick-topped, semi-oval, well-developed rostrum ; in (Edicnemus the 

 grooves overlap slightly above the rostrum. The lips of the grooves are unequally developed, 

 the lower always keeping in the rear of the upper, which is in harmony with their nature as 

 secondary outgrowths. There are four oval xiphoid notches, the outer being much the largest ; 

 and five xiphoid processes ; of necessity the intermediate bars are short, and in Fanellus and 

 (Edicnemus they unite with the middle process so as to convert the original notches into 

 fenestra?. In the latter Bird the outer bars do the same, and the inner fenestrse become broken 

 up into two, one of these often becoming obliterated on one or the other side. In Parrajacana 

 and Scolopax gallinago the inner notches are absent ; they may have existed, however, in the 

 embryo. The outer xiphoid bar of (Edicnemus reaches the end, or nearly so, of the Sternum ; 

 it stops sooner in Vanellus, but in most it ends considerably in front of the middle and inter- 

 mediate bars. This condition is best seen in Numenius and Totanus, and here we get close to 

 those generalised Birds the Sand-grouse (Pteroclinae), which lie but little above the Ostriches, 

 underlie the Pigeons, and have much of the Plover in them (see 'Trans. Zool. Soc./ 1864, vol. v, 

 part 3, pp. 190 205). The keel of the Sternum is very large in all ; it reaches the end, or only 

 flattens out a little near the end of the middle xiphoid bar. In front it retires a little below 

 the rostrum, and then projects elegantly at the angle : this part does not unite with the furcula. 

 Behind the thickened upper coracoid lips there is a deep fossa, which, in Birds with a pneumatic 

 Sternum, would be the air -passage of the keel. Here it shows itself to be merely a remnant 

 of the primordial divisional line of the bone. The upper surface of the Sternum is very hollow ; 

 the bony substance, like that of the rest of the skeleton, is thin, horny, and fatty, and thus has 

 altogether a primordial character. 



